1. Field of the Invention
This invention relates to well tools and more particularly to seal elements for use on multiple packers for wells, such as oil or gas wells, or the like.
2. Related Art and Information
Dually completed wells are so constructed as to permit simultaneous and separate production from two different pay zones. Early dual wells were provided with a single string of tubing and had a single well packer between the two pay zones. The lower zone produced through the tubing and the upper zone produced through the tubing-casing annulus.
Dual completions were later improved to make them easier to control, safer, and more economical. For many years it has been common practice to provide a string of tubing for each of the two pay zones with a packer above each pay zone. Thus, such a well has a single packer between the zones and a dual packer above the upper zone. The short string of tubing extends down through the upper packer to conduct flow from the upper zone to the surface. The long string of tubing extends down through both packers and conducts flow from the lower zone to the surface.
In a similar manner, a triple completion is constructed to produce from three zones simultaneously and has three packers (a single, a dual, and a triple). Quadruple completions may be similarly constructed with four tubing strings and four packers: a single, a dual, a triple, and a quadruple. Quadruple completions are rare. Triple completions are much less common than duals.
In many cases, the seal elements of dual packers have successfully held only moderate pressures without leaking. It has been desirable to provide seals which would hold much higher pressures without leaking.
Applicant is familiar with the following listed prior patents which disclose dual packers, each being hydraulically actuated and each having a central seal element disposed between upper and lower end elements.
______________________________________ 3,167,127 3,288,218 3,381,752 3,851,705 4,413,677 4,505,332 4,512,399 ______________________________________
U.S. Pat. No. 3,167,127 which issued to Phillip S. Sizer on Jan. 26, 1965; U.S. Pat. No. 3,288,218 which issued to Carter Young on Nov. 29, 1966; U.S. Pat. No. 3,381,,752 which issued to Thomas L. Elliston on May 7, 1968; U.S. Pat. No. 3,851,705 which issued to Marion Barney Jett, et al, on Dec. 3, 1974; U.S. Pat. 4,413,677 which issued to Donald H. Perkins on Nov. 8, 1983; U.S. Pat. No. 4,505,332 which issued to Aubrey C.Mills, et al, on Mar. 19, 1985; and U.S. Pat. No. 4,512,399 to John C. Gano and Donald H. Perkins on Apr. 23, 1985, each show a hydraulically actuated dual packer on which is mounted a set of packer seals. This seal set consists of three elements: a central dual element between an upper and a lower end element. These seal sets are obviously well known and have been in use for years, and are of a type which has been known to leak at much lower pressure than has seemed reasonable.
The present invention is an improvement over such seal sets, which improvement enables the seal elements to seal more readily and hold much greater pressure differentials than heretofore. This improvement therefore overcomes a problem which obviously has existed for many years, and does so at very little additional cost. This improvement can eliminate many costly packer failures. Thus it fills a long-felt need in the oil and gas industry.